Ardeipeda egretta Panin & Avram, 1962

Abbassi, Nasrollah, Salehi Tinooni, Mohammad, Ghorbani Dehnavi, Mahdi, Shakeri, Safoora & Eshaghi, Ali, 2024, Oligocene vertebrate footprints from the Lower Red Formation, Central Iran, Fossil Record 27 (2), pp. 265-287 : 265-287

Ichnospecies Ardeipeda egretta Panin & Avram, 1962

Fig. 2 A, B

Materials.

Three footprints in one trackway, sampled specimen, IFMI -680 .

Revised diagnosis.

Avian tracks of moderate size, exhibiting four digits, II to IV directed forward and I backward. All digits are slender and relatively long; digit III is longest, II and IV about four-fifths the length of digit III, digit I about three-fifths the length of digit III. Digit I forms a backward prolongation to the axis of III; the interdigital angle between digits III and IV is greater than that between digits II and III. The digits are united proximally. Trackway moderate; stride moderate in size (emended from Sarjeant and Langston 1994).

Description.

This trackway includes three small tetradactyl footprints, preserved as hyporeliefs on the lower bedding plane of fine-grained sandstone (Fig. 2 , trackway a 1 - a 3). Three-digit imprints ( II-IV) directed forward and a relatively shorter fourth digit (I) directed backward. Digit I imprint is not completely prolonged to the axis of III. Digit imprints are straight, slender, with sharp tips, no claw imprint is visible. Digit imprints connected to each other in the heel imprint. Interdigital angles of II-III and IV-III are not symmetrical, and the angle between digits II-III is closer than that between digit III-IV (Table 1 ).

Discussion.

The studied small bird footprints show slender digit imprints with sharp tips, imprints of digit II and IV are slightly asymmetric relative to the digit III axis, and show a lower interdigital angle II-III compared that of IV-III, thus we considered it as Ardeipeda egretta . Panin and Avram (1962) established Ardeipeda for small to large tetradactyl bird footprints with three ichnospecies, A. egretta , A. gigantea , and A. incerta . These ichnospecies have slender digit imprints with sharp tips. Usually, the digit I imprint is large and directed along the digit III axis, and mostly closer to digit II. Digit IV and II imprints are not symmetrical with respect to the digit III axis, and the interdigital angle II-III is smaller than that of digit III-IV. A. gigantea is a larger footprint with sharp digit tips and relatively thicker digit imprints compared to A. egretta . Ratios of FL / FW and FL / DL I of A. incerta are the same as these ratios in A. egretta , and both footprints have similar morphology, thus A. incerta is considered a junior synonym of A. egretta ( Abbassi et al. in press). Lockley and Harris (2010) suggested the replacement of Avipeda filiportatis under Ardeipeda , but Avipeda filiportatis shows distinctive heel imprints and digit I imprint is not as clearly impressed as the imprints of the other three, so it is not considered to belong to Ardeipeda here. Ardeipeda is attributed to herons ( Abbassi 2022).

Figures

Figure 2. A, B. Ardeipeda egretta, trackway a 1 – a 3 and Gruipeda dominguensis (b), sampled specimen, IFMI - 680; C, D. Aviadactyla vialovi trackway b 1 and Gruipeda dominguensis, trackway a 1 – a 4; mcc – mud crack cast; nvs – non-vertebrate structures; sampled specimen, IFMI - 681.